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How do I delete an exported environment variable?
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unset is the command you're looking for.
unset GNUPLOT_DRIVER_DIR
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If string is empty then return some default value
Often I need to check if some value is blank and write that "No data present" like that:
6 Answers
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String comparison in bash. [[: not found
...ry:
$ bash myscript
or, if the script is executable:
$ ./myscript
sh and bash are two different shells. While in the first case you are passing your script as an argument to the sh interpreter, in the second case you decide on the very first line which interpreter will be used.
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How to upgrade all Python packages with pip?
...finite potential variations for this. I'm trying to keep this answer short and simple, but please do suggest variations in the comments!
In older version of pip, you can use this instead:
pip freeze --local | grep -v '^\-e' | cut -d = -f 1 | xargs -n1 pip install -U
The grep is to skip editable...
Instantiating object of type parameter
...ngBuilder::new);
Alternatively, you can provide a Class<T> object, and then use reflection.
class MyClass<T> {
private final Constructor<? extends T> ctor;
private T field;
MyClass(Class<? extends T> impl) throws NoSuchMethodException {
this.ctor = impl.getCo...
How to generate a Dockerfile from an image?
... -sV=1.36 nginx:latest
It will pull the target docker image automaticlaly and export Dockerfile. Parameter -sV=1.36 is not always required.
Reference: https://hub.docker.com/repository/docker/alpine/dfimage
below is the old answer, it doesn't work any more.
$ docker pull centurylink/dockerfile-from...
Easy idiomatic way to define Ordering for a simple case class
I have a list of simple scala case class instances and I want to print them in predictable, lexicographical order using list.sorted , but receive "No implicit Ordering defined for ...".
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Why should the copy constructor accept its parameter by reference in C++?
...cause if it's not by reference, it's by value. To do that you make a copy, and to do that you call the copy constructor. But to do that, we need to make a new value, so we call the copy constructor, and so on...
(You would have infinite recursion because "to make a copy, you need to make a copy".)
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Javascript Reduce an empty array
...e the array, I am trying to get the number zero, but I dont clearly understand the behaviour of the function
2 Answers
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Finding which process was killed by Linux OOM killer
...@jberryman: For some reason, syslog is in /var/log/syslog on some distros, and /var/log/messages on others. I think it's Debian for the former and Red Hat for the latter, BICBW.
– Tom Anderson
Mar 26 '13 at 11:34
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